An array of laser emitters (e.g., laser diode bar) may be used to produce a high-power laser output by aggregating the laser beams generated by the array of laser emitters. A portion of an example prior art laser system 100 is shown in FIGS. 1A and 1B, which depict a laser diode bar 102, and a micro-optic module 104 comprising a fast axis lens 106, a beam twister 108 and a mounting substrate 110. Ray segments 112 represent the beam paths of the light emitted by the laser emitters of the laser diode bar 102. The length (L), width (W) and height (H) of the micro-optic module 104 are shown in FIG. 1. Example dimensions of a representative micro-optic module are typically on the order of L=12 mm, W=4 mm, and H=1 mm.
The laser beams diverge quickly along a fast axis of the laser bar, and slowly along slow axis, resulting in a beam with an elliptical cross-section. A first optical lens 106, placed parallel to the line of laser outputs, may be used to collimate the fast axis components of the beams. A beam twister 108 may subsequently rotate the beams by 90 degrees. The first optical lens 106 and the beam twister 108 may be mounted on (e.g., bonded to) a base substrate 110 to form the micro-optic module 100. The base substrate is generally a structural component for the optical components (optical lens 106 and beam twister 108).
Further along the propagation path of the laser beam, a second optical lens 114 shown) may collimate the slow axis components of the beams, as shown in FIG. 1C. Following this collimation by the second optical lens 114, a third optical lens 116 may combine the beams from the laser diode bar 102 (and possibly the beams of one or more other stacked laser bars) for insertion into an optical fiber 118 or other target location. For clarity, only three laser emitters and propagation paths are shown in FIG. 1C, although the laser diode bar may include more or fewer laser emitters.
In operation, a fraction the laser light, produced by the array of laser emitters and propagating through the constituent optical components, may be absorbed by the optical components and cause the temperature of the micro-optic module to increase. The temperature increase, in turn, may cause the shape of the micro-optic module to change. As the module heats, geometrical asymmetries and differences in coefficients of thermal expansion (CTEs) of the module components may cause the module to deform. In the absence of such warping, the micro-optical system may produce a beam spot at a specific location and a suitably small size. As the module warps, the beam spot may move from the specific location and become larger (and less focused—i.e., fuzzier). Adjustments to the system may be made to mitigate the location change, but the adjustments may be time consuming and costly, and the loss of focus may be difficult to correct.